6-Substituted oxo and thio-3-nitroimidazo(1,2-b)-pyridazines and methods of preparing same

ABSTRACT

The preparation of 6-substituted oxo or thio-3-nitroimidazo(1,2b)pyridazines which may have a substituent in the 2-position are described. One method is the nitration in the 3-position of the substituted imidazo(1,2-b)pyridazine to give the desired product. Other methods are described. The compounds are useful for their anti-protozoal activity particularly as anti-amebic and antitrichomonal agents.

United States Patent 1 Tomcuecik et al.

[ Sept. 16, 1975 1 6-SUBSTITUTED OXO AND THIO-3-NITROIMIDAZO[1 ,2-b] PYRIDAZINES AND METHODS OF PREPARING SAME [75] Inventors: Andrew Stephen Tomcuecik, Old

Tappan, N.J.; Patrick Thomas 1120; Paul Frank Fabio, both of Pearl River, NY.

[73] Assignee: American Cyanamid Company,

Stamford, Conn.

[22] Filed: Jan. 29, 1974 [21] App]. No.: 437,546

Related US. Application Data [63] Continuation-impart of Ser. No. 293,234. Sept. 28, 1972, Pat. No. 3,828,041, which is a continuation-in-part of Ser. Nos. 118,508, Feb. 24, 1971, abandoned, and Ser. No. 118.510, Feb. 24, 1971, abandoned.

[52] US. Cl. 260/250 AC; 424/250 [51] Int. Cl. C07D 237/26 [58] Field of Search 260/250 AC [56] References Cited UNlTED STATES PATENTS 3,489,755 l/l970 Lombardino 260/250 AC X 3,725.407 4/1973 Tomcufcik et al 260/250 AC Primary ExaminerDonald G. Daus Assistant ExaminerAnne Mlarie T. Tighe Attorney, Agent, or Firm-Ernest Y. Miller 1 1 ABSTRACT 9 Claims, No Drawings 6-SUBSTITUTED OX AND THIO-3-NITROIMIDAZO(1,2-B)-PYRIDAZINES AND METHODS OF PREPARING SAME This application is a continuation-in-part of application Ser. No. 293,234, filecl Sept. 28, 1972, now U.S. Pat. No. 3,828,041 which in turn is a continuation-inpart of application Ser. Nos. 118,508, filed -Feb. 24, 1971, now abandoned and application Ser. No. 118,510, filed Feb. 24, 1971 now abandoned.

SUMMARY .oF THE INVENTlON This invention relates to 6-mono or 2,6-disubstituted 3-nitroimidazo[l,2-blpyridazines and methods of preparing the same. f

The compounds of this invention may be illustrated by the following formula: 1 t

whereinR is hydroxy, mercapto,'alkoxy (C -C alky1 thio (C -C phtlialimidoloweralkoxy, phenylloweralkoxy, lower alkylaminoloweralkoxy, lower alkoxyloweralkoxy, hydroxylower'alkoxy, lower alkenyloxy, halobenzoylloweralkoxy "and R is hydrogen or lower alkyl. ,1

In the above compounds, lowei'alkyl arelthose'hav ing 1 to 4 carbon atoms: loweralkenyl those having 2 to 4 carbon atoms; lower alkox'y'tho s'e having 1 to 4 carbon atoms; lower alkanoyl those having 1 to 4 carbon atoms in addition to the carbonyl group and halo those having chlorinej bromine, iodine and flourine present. The compounds are in general, crystalline.

The present compounds can be preparedby thefollowing methods: Y

A. The I reaction of 6-mono or 2,6- disubstitutedimidazo[ l,2-b]pyrid azines with nitric and sulfuric acid which can be illustrated as follows:

R- \N/N N02 2 wherein R and R, are as defined hereinbcfore and X is oxygen or sulfur, Y is halogen and Z is an alkali metal. This reaction is preferably carried out in a solvent such ,as methanol, ethanol, propanol, butanol, dioxane and the like. The temperature at which the reaction is conducted is not critical and may vary from 15C. to about 60C. no advantage is generally noted by carrying out the reaction aboveroom temperature.

C. The reaction of a 6-alkali metal oxo or thio-2- substitutedor unsubstituted 3-nitroimidazo[ 1,2- b']pyridazine with a halogen compound is illustrated as follows:

are measured by means of an assay devised from W. R, Jones, The Experimental Infection of Rats with Ema-- moeba Histolylica and a Method for Evaluating the Anti-Amoebic Properties of New Compounds, Annals of Tropical Medicine and Parasitology, volume 40, pages -140 (1946). The assay is carried out as follows:

The test organism is Entambeba histolytic NIH 200 u. Cultures are maintained on Cleveland Collier liver infusion medium with serum saline 1:1 overlay in 3 X 5 test tube slants. Rice powder is added as a growth factor. Cultures are transferred at 5 day intervals and kept at 37C. A 48 hour culture is used for the test inoculum and harvested the morning of the test by collecting the sediment containing rice powder and amoebae found at the junction of the butt and the slant. The amoebae are counted and the amount of inoculum for injection is adjusted to contain approximately 200,000 to 250,000 amoebae. Female Wistar strain albino rats from the Royalhart Farms weighing 20-35 grams are used. The cecum is exposed during laporatomy and the amoebaerich inoculum is injected into the anterior section. The incision is closed with autoclips. Procedures are sterile throughout the course of the surgery. The infected rats are divided randomly into groups of l0. Treatment is begun on the day of infection. Drugs are premixed in a standard laboratory feed sold as Purina Lab. Chow by the Ralston Purina Company. Rats are maintained on the drug diet for five days at the end of which they are necropsied and the cecum examined both macroscopically for pathologic feature of infection and microscopically for the presence of amoebae. Scores of one each are recorded for evidences of mucous, fibrosus, and lesions of inflammation. A score of one is recorded for a finding of 1-2O amoeba and a score of 2 for a finding of more than 20 amoeba on a standard slide preparation. Total score of -5, thus, is possible per rat at necropsy. The arithmetic mean of the combined A.D.l.s (Average Degree of Infection in a test orcontrol group of rats is considered to be the group ADI.- Activities are expressed in percent of suppression of group ADl of a test group to the group ADI or a control group. Consumption of test compound is: determined from the weight of feed consumed. For example, the compounds 6-methoxy-3-nitroimidazo[1,2-b]pyridazine and 6- ethoxy-3-nitroimidazo[l,2-b]pyridazine have a minimum effective dose (60% supp. of control ADI) mg./kg./day X 5 of about 30.

The following Table I shows the amebicidal activity of representative 6-oxo-, thioor substituted oxo or thio compounds of the present invention.

TABLE 1 The action of imidazopyridazincs against experimental intestinal amcbiasis in rats All compounds are tested initially to 0.025% drug concentration in the diet (approximately mg./kg./day X 5) Minimum effective dose supp. of control A.D.l.) mg./kg./day X 5 The present compounds have shown activity as trichomonicides in tests designated to detect this activity. One such test is carried out as follows:

Female albino mice (Royalha'rt' lCR' strain) are inoculated subcutaneously'with 50,000 to 100,000 Tri chomonas vaginalis" Thom's strain) suspended in a cysteine-peptone-liver infusion maltose medium described by-Garth Johnson and Ray E. Trussell, Experimental Basis for the Chemotherapy of Trichomonas vaginulis Infestations l-; Proceedings of the Society for Experimental Biology and=Medicine Volume 54, pages 245-249 1943): In control animals, approximately one week postinoculation, the site of inoculation is marked by a subcutaneous abcess which contains numerous trichomonads in a menstruum of pus. ln effectively treated animals theabcesses are either undetectable or greatly reduced in'size, and motile trichomonads cannot be detected in the lesion-derived material after prolonged microscopic examination. Pressure of a single motile trichomad after treatment is recorded as a negative result.

Treatment by test drugs consists either of one or more oral doses suspended in 0.2% agar and administered by gavage one day post inoculation, or by administration in the diet for five consecutive days beginning one day postinoculation. The diet is a commercial laboratory feed sold as l urina Lab, Chow by the Ralston- Purina Company. .Thetest compound is mixed thoroughly in the carrier, 0.2% agar, 0.5% carboxymethylcellulose or ground laboratory-feed. Each regimen is administered to a test group consisting of five or 10 mice. Control groups of five or 10 mice receive the carrier alone. .Gavage doses are estimated for the average mouse" weight obtained just beforedosing. Drug intakes resulting. from diet.;therapy are estimated for average mouse weightsand total group feed intakes during the treatment period. Avtivities of many compounds of the presentinvention in this test are comparable to that of Z-mejthyl-S-nitro-l-imidazoleethanol, as vvell recognized commercial trichomonicide. The following Table ll shows the activity against Trichomonas vaginalis of representative compounds of the present invention.

TABLE 11 The action of representative nitroimidazopyridazines of the present invention against subcutaneous 'I'rit'lmnmmls vagina/ix infections in mice (om pound No. Cleared"/No, treated after a single gavage dose of mg./l g.

(v-Methoxy-f -nitroimidaxol I .Z-b lpyridaline 6-l-'.thoxy-3-nitroimidazol LZ-blpyridazine 6-Hytlroxy-3-nitroimidazol LIZ-h]- pyridaline o-Methoxy-l-niethyl- 3-nitroimitlalol l,2-h]pyrida'/.ine o-nButoxy-3-nitroimidazol LZ-h lpyridazine (v-Allyloxy-fi-nitro imidaxol l.2-h|- pyridazine (1-( 2-Dimethylaminoethoxy)-3-nitroimidalu| LIZ-h]- pyridazine (1-( Z-Ethoxyethoxy B-nitroimidazol LIZ-b pyritlavinc 6-lsopropox \'-3- nitroimidazol l.2-h]- pyritlazine TABLE 11 -Continued The action of representative nitroimidazopyridazines of the present invention against subcutaneous 'l'rivlmmmzru \llgl llll/[A infections in mice No. Clcarcd"/No. treated after a single gavagc dose of mg. g.

Compound 100 50 25 12.5 6.2 3.

6-n-Propoxy-3- /10 10/10 9/10 3/10 nitroimidazo[ l,2-b]- pyridazinc t')-( Z-Hydroxy 10/ l 0 fi/ 1 (J 6/10 6/10 cthox \*)-3-nitruimidalo] l ,Z-hlpyridazinc Compositions containing the 6-mono or 2,6- Analysis: Calcd. for C H N 0 C, 43.30; H, 3.12; N,

disubstituted-3-nitroimidazo[ l,2-b]pyridazines may be administered to warm-blooded animals orally, or parenterally if desired, and when so administered, may be considered as an agent for therapeutically desirable treatment of amebic or trichomonal infections in daily doses ranging from about 0.5 mg. to about 30 mg. per kilogram. The dosage regimen can be adjusted to provide optimum therapeutic response. Thus, for example, several smaller doses may be administered daily, or the dose may be reduced or increased proportionately as indicated by the requirements or the particular thera peutic situation. v

For therapeutic administration the active compounds of this invention may be incorporated with pharmaceutical acceptable carriers such as excipients and used, for example, in the form of tablets, dragees, capsules, suppositories, liquids, elixirs, emulsions, suspensions or the like. Such compositions and preparations should contain at least 0.1% active component. The percentage in the compositions and preparations, may of course, be varied, and may conveniently be between 2% and 60% or more of the weight of the unit. The

amount of compound in such therapeutically useful compositions or preparations is such that a suitable dosage will be obtained. Preferred compositions or preparations according to the present invention are prepared so that a dosage unit form contains between about 10 and about 300 milligrams of the active compound. Obviously, in addition to the therapeutic compound, there may be present excipients, binders, fillers and other therapeutically inert ingredients necessary in the formulation of the desired pharmaceutical preparation.

SPECIFIC DESCRIPTION The following examples describe in detail the preparation of representative compounds of this invention and formulations using said compounds.

EXAMPLE 1 Preparation of 6-Methoxy-3-nitroimidazo[ l,2-b]pyridazine A. Seven grams of 6-methoxyimidazo[ 1,2- b]pyridazine (J. G. Lombardino, .I. Het. Chem. 5 35 1968)) is added in small portions to 21 ml. of concentrated sulfuric acid, the temperature being held below 10C. by external cooling. The resultant solution is stirred and the temperature maintained below 13C. by external cooling as 7.3 ml. of 70% nitric acid is added dropwise. The reaction mixture is allowed to warm to room temperature and stirred for an additional hour. It is then drowned into 150 ml. of ice and water. The pale yellow precipitate is collected, washed free of acid with cold water, and dried. Recrystallization from ethanol gives 4.0 grams of pure product melting at 152.5154.5C.

28.86.Found: C, 43.16; H, 3.19; N, 29.04.

B. Alternatively, the above compound is prepared by warming equimolar quantities of 6-chloro-3- nitroimidazo[l,2-b]pyridazine and sodium methoxide dissolved in a solvent (such as, methanol, dioxane, dimethylformamide) until completion of the reaction. The solvent is removed under reduced pressure and inorganic salts by washing with water. Purification is carried as described in A above.

C. The subject compound can also be prepared by stirring a suspension of the sodium salt of 6-hydroxy3- nitroimidazo[ l,2-b]pyridazine (Example 3) in dimethylformamide with an excess of methyl iodide until a clear solution is obtained. Isolation and purification is effected as described in A above.

EXAMPLE 2 Preparation of 6-Ethoxy-3-nitroimidazo[ l,2-b]pyridazine The preparation of the subject compound is carried out essentially as described in the procedure of Example lA,' an equivalent of 6-ethoxyimidazo[ l,2- b]pyridazine replacing the 6'methoxyimidazo[1,2- b]pyridazine. After recrystallization from ethanol, the compound melts at 14915lC.

Analysis: Calcd. for C H N O C, 46.15; H, 3.87; N, 26.92. Found: C, 46.13; H, 3.78; N, 27.00.

EXAMPLE 3 Preparation of 6-Hydroxy3-nitroimidazo[ l,2b]pyridazine A solution of 5.4 grams of 6-hydroxyimidazo[ 1,2- b]pyridazine in 50 ml. of concentrated sulfuric acid is stirred at room temperature as 5 ml. of red fuming nitric acid is added dropwise. The mixture is then stirred and heated on the. steam bath for 6 hours. After cooling to room temperature, the solution is poured into 500 grams of ice and water. The pale yellow precipitate is collected, washed free of acid, and dried. Recrystallization from a mixture of ethanol and dimethylformamide gives 2.8 grams of pure product, melting at 305310C. with decomposition.

Alternatively, the subject compound is prepared by heating the compound of Example 1 with 48% hydrobromic acid at reflux for 16 hours, followed by removal of the aqueous acid under reduced pressure, and purifi cation of the residue as described above.

Analysis: Calcd. for C ;H,,N ,O C, 40.01; H, 2.24; N. 31.11. Found: C, 39.55; H, 2.16; N, 30.96.

EXAMPLE 4 Preparation of 6-Methoxy-2-methyl-3-nitroimidazo[ 1 ,2-b]pyridazine The title compound is prepared essentially by the procedure of Example 1A an equivalent of 6-methoxy- 2-methylimidazo[1,2-b]pyridazine (prepared as described by J. G. Lombardino, J. Het. Chem. 35 (1968)) replacing the 6-methoxyimidazo[l,2- b]pyridazine. Recrystallization from ethanol gives the pure compound, melting at l70173C.

Analysis: Calcd. for C H N O C, 46.15;'H, 3.87; N, 26.92. Found: C, 46.14; H, 4.04; N, 27.01.

EXAMPLE 5 Preparation of 6-Methylthio-3-nitroimidazo[ l,2-b]pyridazine Methyl mercaptan is bubbled througha solution of 016 gram of sodium methoxide in 50 ml. of methanol for minutes. Two *grams of 6-chloro-3- nitroimidazo[1,2-b]pyridazine is then added, and the mixture placed in a stoppered flask and stirred for 2 hours. The precipitate present is'collected, vwashed with water, dried, and recrystallized from ethanol to give the pure compound, melting at -174-176C.; yield, 1.9

grams. i 7

Analysis: Calcd. for C H N SO f C, 40.00; H, 2.88; N, 26.66. Found: C, 40.24; H, 2.91; N, 26.91.

' EXAMPLE 6 1 Preparation of 6-n-Butoxy-3-nitroimidazo[ l ,2-bjpyridazine EXAMPLE 7 Preparation of 6-Benzyloxy3nitroimidazol 1,2-b Ipyridazine One and six-tenths grams of 50% sodium hydride dispersion in mineral oil is added to a solution of 3.45 ml. of benzyl alcohol in 100 ml. of dioxane. The mixture is stirred at room temperature until gas evolution ceases. 6.0 grams of 6-chloro-3-nitroimidazo[1,2-b1pyridazine is added to the mixture, which is stirred until reaction is completed. The precipitate is collected,-washed with water, and dried. Recrystallization from ethanol gives 19 grams of the pure compound, melting at 155.5l57.5C. 1

Analysis:'Calcd. -for C gHu NqOaZ C, 57.77; H, 3.37; N, 20.73. Found: C, 58.13; H, 3.72; N, 20.99.

EXAMPLE 8 Preparation of 6-(Carbethoxymethoxy)-3-nitroimidazo[1,2-

b]pyridazine A stirred solution of 7.2 grams of 6-hydroxy-3- nitroimidazo[ l,2-b]pyridazine (Example 3) in 200 ml. of dry dimethylformamide is treated with 2.5 grams of 95% sodium methoxide. After fifteen minutes, the thick yellow suspension of the sodium salt of the starting compound is treated with'7.5 ml. (excess) of ethyl bromoacetate. A clear solution is obtained in 2 hours.

After stirring for an additional fourteen hours, the solution is concentrated to dryness under reduced pressure.

Inorganic salts are removed by extraction with 250 m1. of water. The insoluble residue is recrystallized from ethanol, yielding 7.6 grams of the subject compound, melting at 123124C.

Analysis. calcd. for C H N O c, 45.11; H, 3.79; N, 21.05. Found: C, 44.80; H, 3.73; N, 21.39.

EXAMPLE 9 Preparation of 6-Allyloxy-3-nitroimidazo[ 1,2-b]pyridazine The above compound is prepared essentially by the procedure of Example ,8, 4.9 grams of allyl bromide replacing the ethyl bromoacetate. After recrystallization from ethanol, 4.1 grams of pure compound is obtained, melting at 124125C.

Analysis Calcd. for C H N O C, 49.09; H, 3.66; N, 25.44. Found: C, 48.30; H, 3.52; N, 25.62.

EXAMPLE 10 Preparation of 6-(p-Chlorophenacyloxy)-3-nitroimidazo[ 1,2- b]pyridazine The subject compound is prepared essentially by the procedure of Example 8, 7.3 grams of 2-bromo-4- chloroacetaphenonereplacing the ethyl bromoacetate. After recrystallization from a mixture of ethanol and dimethylformamide, 4.7 grams of the pure compound is obtained, melting at 223-225C. with decomposition. Analysis Calcd. for c,,H,N,o,c1; c, 50.54; H, 2.73; CI, 10.66. Found: C, 50.63; H, 2.67; Cl, 11.06.

EXAMPLE 1 1 Preparation of l,2-Bis(3 nitroimidazo[1,2-blpyridazine-6-yloxy)-ethane The subject compound is prepared essentially by the procedure of Example 8, 3.7 grams of 1,2- dibromoethane replacing the ethyl bromoacetate. After recrystallization from a mixture of ethanol and dimethylforrn'amide, the product melts at 257259C. with decomposition.

Analysis Calcd. for C H N O C, 43.33; H, 2.61; N, 29.01. Found: C, 43.70; H, 2.82; N, 29.50.

. EXAMPLE 12 Preparation of 6-( 2-Ethoxyethoxy )-3-nitroimidazo[ 1 ,2b]pyridazine The subject compound is prepared essentially by the procedure of Example 8, 5.6 grams of 2- bromodiethylether replacing the ethyl bromoacetate. After recrystallization from ethanol, 39 grams of pure product is obtained, melting at 125126C.

Analysis Calcd. for C H N O C, 47.62; H, 4.80; N, 22.21. Found: C, 47.56; H, 4.55; N, 22.45.

EXAMPLE 13 Preparation of 6-( 2-Dimethylaminoethoxy )-3-nitroimidazo[ 1,2- b]pyridazine hydrochloride The free base of .the subject compound is prepared essentially by the procedure of Example 7, 3.0 grams of 2-dimethylaminoethanol replacing the benzyl alcohol. Thisis dissolved in acetone and treated with a slight excess of hydrogen chloride in isopropanol solution. The resultant yellow precipitate is recrystallized from methanol to yield 2.3 grams of the pure-compound, melting at 223226C. (with decomposition). Analysis Calcd. for C H N Q HCl: C, 4l .74;-H, 4.90; N, 24.34; Cl, 12.32. Found: C, 41.81; H, 4.99;..N, 24.25; Cl, 12.55.

EXAMPLE 14.,

Preparation of 6n-Propyloxy-3-nitroimidazo[ l ,2-b1pyridazine I The above compound is prepared essentially by the procedureof Example 6, 100 ml. of N-propanol replacing the N-butanol. Recrystallization of the product from 400 ml. of methanol gives 47 grams of the pure compound, melting at 161-164C.

Analysis: Calcd. for c,,H,.,N,o c, 48.65 H, 4.54; N, 25.27. Found: C, 48.61; H, 4.52; N, 25.44.

EXAMPLE 1 5 Preparation of y 3 6-lso-Propyloxy-3-nitroimidazo[ l ,2-b]pyridaz ine The subject compound is prepared essentially by the procedure of Example 6, 100 ml; of iso-propanol replacing the N-butanol. Recrystallization from 200 ml. of methanol gives 4.5 grams of the pure compound, melting at l54-l57C.

Analysis: Calcd. for C H N O C, 48.65; H, 4.54; N, 25.22. Found: C, 48.61; H, 4.43; N, 25.47.

EXAMPLE 16 Preparation of 6-( Z-Hydroxyethoxy )-3-nitroimidazo[ 1 ,2-blpyridazine EXAMPLE 17 Preparation of 6-n-Octyloxy-3-nitroimidazo[ 1,2-b]pyridazine The subject compound is prepared by the procedure described in Example 8, an equivalent of 1- bromooctane replacing the ethyl bromoacetate. The reaction is brought to completion by a final heating for 2 hours on the steam bath. Recrystallization from 150 ml. of ethanol gives 3.1 grams of the pure compound, melting at 6567C.

Analysis: Calcd. for C H N O C, 57.52; H, 6.90; N, 19.17. Found: C, 57.15; H, 6.80; N, 19.16.

EXAMPLE 18 Preparation of 3-Nitro-6-( 2-phthalimidoethoxy)imidazo[ 1,2- b lpyridazine The above compound is prepared essentially by the procedure of Example 8, an equivalent of N-( 2-bromoethyl)phthalimide replacing the ethyl bromoacetate. The reaction is brought to completion by heating on the steam bath for 4 hours. Recrystallization from 250 ml. of 2-methoxyethanol gives 2.9 grams of purified 10 compound, melting at 2"602 65 C. with decomposition. V

Analysisz calcd for c' u m og; c, 54.39 H, 3114; N, 19.82. Found: C, 53.93; H, 3.08; N, 19.51. 7

EXAMPLE 19 Preparation of Hard Shell Capsules containing I 6-methoxy-3-nitroimidazo[ 1 ,2-b]pyridazine Per 1000 Capsules g.

6-mcthoxy-3nit'roimidazo 20010 i l-l'.2b]pyridazinc .1 5 1 A Lactose 7 900.0 Magnesium stearatc 10.0

The ingredients are blended together. The mixture is used to fill hard shell capsules of a suitable size each containing 200 mg. of active compound.

EXAMPLE 20 Preparation of Tablet Compositions containing 6-n-butoxy-3-nitroimidazo[ l ,2-b]pyridazine Per 1000 Tahlcts g.

6-n-butoxyimidaz0l l,2-h]- 100.0 pyridazine Corn starch USP 300.0 Dibasic calcium phosphate 2150.0 Magnesium stcaratc 600.0

EXAMPLE 21 Suppositories containing 6-n-propoxy-3-nitroimidazo[ l,2-b]pyridazine 30 suppositories g.

6-n-propoxy-3-nitrol5 imidzizol l ,2-b lpyridazinc Purified water qsAD 20 Gelatin granular 40 Glyccrin Add the water to the medicinal substance to make 20 g. and dissolve or mix together. Add the glycerine and mix well. To the mixture add the gelatin carefully avoiding incorporation of air and heat on steam bath until gelatin is dissolved. Pour the melted mixture into 30 chilled molds and allow to congeal. Each suppository contains 500 mg. of therapeutic component.

EXAMPLE 22 Preparation of Hard Shell Capsules containing 6-( 2-hydroxyethoxy )-3-nitroimidazo[ 1 ,2'blpyridazine Per 1000 Capsules g.

6-( Zhydroxycthoxy )-3- 200.0 nitroimidazol 1 ,2-b]- pyridazine Lactose 900.0 Magnesium stcarate 10.0

The ingredients are blended together. The mixture is used to fill hard shell capsules of a suitable size each containing 200 mg. of active component.

EXAMPLE 23 Preparation of Tablet Compositions Containing 6-ethoxy-3nitroimidazo[ l .2-b]pyridazine per I000 Tablets g.

-cthoxy-S-nitmimidazo- I000 LZ-blpyridazine Corn starch USP 300.0 Dibasic calcium phosphate 2150.0 Magnesium stearatc 600.0

wherein R is hydroxy, C C, alkoxy, methylthio,

12 phthalimido C,C -alkoxy, phenyl C -C alkoxy, C C,- dialkaylamino-C -C -alkoxy, C,C -alkoxy monohydroxy-C C -alkoxy, 0r allyloxy and R, is hydrogen or C -C alkyl.

2. The nitroimidazopyridazine in accordance with claim 1, 6-(Z-hydroxyethoxy)-3-nitroimidazo[1,2- b ]pyridazine.

3. The nitroimidazopyridazine in accordance with claim 1, 6-methoxy-3-nitroimidazo[ l ,2-b]pyridazine.

4. The nitroimidazopyridazine in accordance with claim 1, 6-n-propoxy-3-nitroimdazo[ l ,2-b]pyridazine.

5. The nitroimidazopyridazine in accordance with claim 1, 6-ethoxy-3-nitroimidazo[ l ,2-b ]pyridazine.

6. The nitroimidazopyridazine in accordance with claim 1, 6-n-butoxy-3-nitroimidazo[ l,2-b]pyridazine.

7. The nitroimidazopyridazine in accordance with claim 1, 6-hydroxy-3-nitroimidazo[ l ,2-b]pyridazine.

8. The nitroimidazopyridazine in accordance with claim 1, 6-isopropoxy-3-nitroimidazo[ 1,2- b]pyridazine.

9. The nitroimidazopyridazine in accordance with claim 1, 6ethoxyethoxy-3-nitroimidazo[ 1,2- b]pyridazine. 

1. A NITROIMIDAZOPYRIDAZINE OF THE FORMULA:
 2. The nitroimidazopyridazine in accordance with claim 1, 6-(2-hydroxyethoxy)-3-nitroimidazo(1,2-b)pyridazine.
 3. The nitroimidazopyridazine in accordance with claim 1, 6-methoxy-3-nitroimidazo(1,2-b)pyridazine.
 4. The nitroimidazopyridazine in accordance with claim 1, 6-n-propoxy-3-nitroimdazo(1,2-b)pyridazine.
 5. The nitroimidazopyridazine in accordance with claim 1, 6-ethoxy-3-nitroimidazo(1,2-b)pyridazine.
 6. The nitroimidazopyridaziNe in accordance with claim 1, 6-n-butoxy-3-nitroimidazo(1,2-b)pyridazine.
 7. The nitroimidazopyridazine in accordance with claim 1, 6-hydroxy-3-nitroimidazo(1,2-b)pyridazine.
 8. The nitroimidazopyridazine in accordance with claim 1, 6-isopropoxy-3-nitroimidazo(1,2-b)pyridazine.
 9. The nitroimidazopyridazine in accordance with claim 1, 6-ethoxyethoxy-3-nitroimidazo(1,2-b)pyridazine. 